This invention is concerned with blood-collecting tubes capable of collecting blood and separating it at the same time.
Conventionally, blood collection and separation have involved the processes of withdrawing blood by means of a syringe, for instance, injecting the collected blood into test tubes, mounting the test tubes in a centrifugal separator, and operating the centrifugal separator to separate the blood into its cellular and plasma components by using a difference in their relative densities. This method has one drawback, however, in that it requires a great deal of time and labor from the start of blood collection up to the end of blood separation, because blood collection and separation must be carried out by using completely different facilities.
Under this circumstance, there has been a move in recent years to develop blood-collecting tubes which make it possible to separate blood immediately where it was collected. As an example, Japanese Official Gazette No. 2526889 for utility model applications discloses a blood-collecting tube which is constructed such that a partition plate is provided in a main tubular body, dividing it into an upstream compartment and a downstream compartment, both ends of U-shaped, porous hollow-fiber membranes are attached to the partition plate, their both ends opening to the upstream compartment, and a vacuum is created in the internal space of the main tubular body. When blood is sucked into the upstream compartment of this tube through a blood-drawing needle, the pressure in the upstream compartment increases by an amount corresponding to the amount of the blood drawn into the upstream compartment, and this causes a pressure difference between the upstream and downstream compartments. Due to this pressure difference, the blood enters the lumen of each hollow-fiber membrane through its openings at both ends. Since the hollow-fiber membranes allow only the plasma components of the blood to pass through, the blood is separated into the cellular components in the upstream compartment and the plasma components in the downstream compartment on both sides of the partition plate.
This blood-collecting tube, however, is associated with problems to be solved as cited below:
1) The manufacture of this blood-collecting tube involves the need to perform such work as fixing a large number of U-shaped hollow-fiber membranes to the partition plate and fixing the partition plate at a specified position within the main tubular body. This requires a great deal of effort and makes it impossible to avoid high costs.
2) To examine the plasma components which have flown into the downstream compartment, it is necessary to first suck the plasma components out of the downstream compartment by using another instrument (e.g., a syringe) and then inject the plasma components into a separate vessel (e.g., a test tube). Therefore, there is such inconvenience that even when the plasma components have been successfully separated, subsequent collection of the plasma components could require much time.
3) Although a large number of hollow-fiber membranes are used, they provide a limited surface area since each hollow-fiber membrane has a filament-shaped structure and, thus, blood separation takes substantial time. Furthermore, the hollow-fiber membranes are apt to cause clogging within themselves.
An object of this present invention is to solve the aforementioned problems.
In order to fulfil the above object according to this invention, a blood-collecting tube comprising: an upstream tube having a blood inlet and a blood outlet; a plug fitted to the blood inlet of the upstream tube for closing the upstream tube, the plug adapted for being pierced by a blood-drawing needle; a filter for covering the whole area of the blood outlet of the upstream tube and for separating blood into cellular and plasma components; and a downstream tube for enclosing the filter and the blood outlet and the interior of the downstream tube is sealed, and the downstream tube is attachable to and detachable from the upstream tube.
According to the blood-collecting tube, it is possible to carry out blood collection and separation in an efficient manner by the following procedure:
(1) The interior of both the upstream tube and the downstream tube is depressurized by piercing the plug with a suction tube, for instance. This depressurizing operation may be performed immediately before shipment. More specifically, each blood-collecting tube may be delivered after it has been depressurized by a manufacturer.
(2) After sticking one end of the blood-drawing needle into a blood vessel, its other end is passed through the plug. At this point, blood automatically flows into the upstream tube due to a negative pressure within the upstream tube, and a pressure difference corresponding to the amount of the blood drawn in is produced between the upstream tube and the downstream tube. Due to this pressure difference, the blood gains a tendency to flow into the downstream tube through the blood outlet. However, because the filter is disposed at the blood outlet and only the plasma components are allowed to pass through the filter, the plasma components are separated from the cellular components and flow into the downstream tube. Thus, separation of the blood is performed at the same time as it is being collected. This invention, however, is not necessarily limited to blood-collecting tubes designed to separate the blood into its cellular and plasma components in an extremely strict fashion but includes those which allow quite a limited portion of the cellular components having relatively small diameters (e.g., platelets) to pass through the filter.
(3) Upon completion of blood collection, the downstream tube is removed from the upstream tube. Since only the plasma components have been collected in this downstream tube, the downstream tube can be used as it is as a test tube in subsequent examination.
Other objects, features and advantages of the present invention will become readily apparent from reading of the following description which has been prepared in conjunction with the accompanying drawings.